Transmission temps on ScanGauge D

[Sky_Boss]

Originally Posted by JEEPOHOLIC

I have a scan gauge d on my 1999 freightliner fl-60 with a 7.2 cat motor and a md3060 allison transmission, my truck weights about 13,000, the transmission has about 200 miles on it from the rebuild, my dash trans gauge reads about 190-200 deg F while bob tailing, the scan gauge reads 120 degs F while bob tailing, the engine temp is about 190 deg F, now with all that info should I be concerned about the 80 or so degs difference ?

80* temp difference seems a bit much to me but my experience is with my Cummins ISL and MH3000 tranny.

FWIW, My Scan D seems to be pretty close to the analog gauge both for water and tranny fluid. Pretty much I see 200*-202* water temp when charging hard and 202*-204* (+2* from water temp normally) for tranny fluid. Even on cool/cold days my water these temps are pretty normal but both will drop quicker on downhills and long deceleration times.

I don't see any issues with those temps and my tranny fluid analysis has come back just fine for the last 2 years.

[akeyzoo]

I am with sky boss, something is amiss with your temps. Mine match his exactly, and my Allison once warm sticks to 202 no matter the load.

Perhaps a sending unit? My fear with such a low reading is that it may have your tranny running in a "cold mode" if that exists. My guess is that the actual temperature is closer to 200.

Worth investigating.

Chris

[cees]

well mine has reached 240F
after climbing mont blanc in europe

Cees

[Dtwallace]

I would suspect the Scan Gauge to be too low on it's indication. You should have a thermostat in the system to help maintain a normal temperature range close to what your dash temp gauge is showing you. As I would expect a rise like what (CEES) described in a long climb, and that 240F should not go much higher as the heat exchanger (if you have that type of trans cooler) will take some of that heat and transfer it to the engine cooling system, you'll see the engine temp rise as well. All this is part of the normal operation, but still requires you monitor the temps and take corrective action in case of an over temp.. 240F for long periods of time is not good and should be avoided.

[johnzuki]

2000 Freightliner Winnebago 36'. I do not get a trans temp readout, but everything else is there. I just assume it does not report trans temp on this unit.

[dbarton291]

Originally Posted by Elictrix

Analogue transmission gauges are usually connected to the oil outlet pipe from the transmission to the oil cooler. This is called converter out.

Digital displays read the transmission sump temperature broadcast by the ECU.

Converter out temperature will be higher than the sump temperature if the oil cooler is doing its job.
Analogue gauges are indicators and may not be too accurate. They give an indication of what the temperature is.

With all gauges and displays you need to learn what they normally read, and be able to spot when one is reading differently from normal.

This info is dead on accurate. Do you work for or have worked for an Allison dealer or distributor? The terms you use indicate you have an in depth knowledge of Allison transmissions.

[Elictrix]

Lets just say that I have quite a few Allison training certificates.

[dbarton291]

Originally Posted by Elictrix

Lets just say that I have quite a few Allison training certificates.

That works for me!